At present, USB Type C interface is widely used and can transmit DP, USB，PCIE， Audio and other signals are no longer purely used for transmitting USB signals, that is, USB Type C has freed itself from its subordinate relationship with USB and taken charge of its own affairs. Below are some important points in USB Type C.
The latest protocol "USB Type-C Specification Release 1.4. pdf" can be downloaded from the official USB website. The main content of this protocol is to define the plug, socket, and cable of USB Type C; Detection and use of Vbus current for USB Type-C; Using a USB Type-C source (host or downstream hub port) can achieve higher source current on VBUS, allowing for faster charging of mobile devices or power supply devices that require more current than specified in the USB 3.2 specification. All USB hosts and hub ports are set to the current available level through the CC pin; The power supply capabilities of various modes of USB PD are shown in the following table:
The Type-C interface has male and female sockets, as shown in the following figure:
VBUS, the bus power of the USB cable (consistent with our usual VBUS), has 4 wires for power and GND, which is why it can support up to 100W. VCONN (only available on the plug) is used to supply power (3.3V or 5V) to the chip in the cable when there is a chip in the cable. USB 2.0 data cable, D+/D-。 They only have one pair on the plug end, which is consistent with the old USB 2.0 specification. But in order to support arbitrary insertion in both directions. Two groups are defined at the socket end, so that the socket end can be mapped appropriately according to the actual situation. USB 3.1/USB 3.2 data cables, TX+/- and RX+/-, used for high-speed data transmission. There are two sets of plugs and sockets, which are used to support free insertion in both directions. For the signal of Configuration, there is only one CC for the plug, and another pseudo VCONN. For the socket, there are two CC1 and CC2. SUB signal, used for USB expansion function, can be used for analog audio. USB4 E-mark Chip Science Popularization
As shown in the table below, the cable length for USB 2.0 specification is less than 4 meters, USB 3.2 Gen1 is less than 2 meters, and USB 3.2 Gen2 is less than 1 meter.
Full function USB Type-C cable signal instructions
The figure shows a standard USB Type-C cable, with high-speed signal differential pair SDP using coaxial lines, and signal ground return through shielding GND.
As shown in the figure below, if the Type-C cable is only used for USB function, there are actually many signal lines that are not needed, only the following signals are needed (except for USB3.2 Gen2x2). USB 2.0 requires fewer cables and does not require 5-10 signals
The association standard does not specify conductor specifications. Thicker wires cause less attenuation, but at the cost of larger overall cable diameter and reduced flexibility. Multiple wires can be used for a single wire, such as Vbus or ground. It is recommended to use the smallest wire size to meet the requirements of cable assembly, electrical, and mechanical. In order to maximize the flexibility of the cable, the outer diameter of the cable should be minimized as much as possible. A typical USB full-featured Type-C cable has an outer diameter ranging from 4mm to 6mm, while a typical USB 2.0 Type-C cable has an outer diameter ranging from 2mm to 4mm. A typical USB Type-C USB 3.1 cable can have an outer diameter ranging from 3mm to 5mm.
The impedance of the SDP shielded differential line is controlled at 90 Ω± 5 Ω, and the impedance of the single ended coaxial line is controlled at 45 Ω± 3 Ω. Impedance should be evaluated using a rise time of 200 ps (10% -90%). Power supply VBUS and GND; As shown in the figure below, the voltage drop of the power supply should be less than 500mV, and the voltage drop above Gnd should be less than 250mV
CC pin configuration channel popular science
The purpose of configuring channel CC is as follows:
Check if the USB device is connected; Detect the direction of USB insertion and establish a route for the USB data channel based on this; Assist in establishing USB device roles after insertion (who is the HOST and who is the Device); Discover and configure VUBS, configure USB PD power mode;
Configure Vconn; Discover and configure optional backup and auxiliary modes;
DEFINITION
In the USB 2.0 port, USB defines three roles based on the direction of data transfer: HOST/Device/OTG. Among them, OTG can be used as either HOST or Device, and there is a similar definition in Type-C.
DFP(Downstream Facing Port)： The downstream port can be understood as Host or HUB, DFP provides VBUS VCONN， Can receive data. In the protocol specification, DFP specifically refers to the downlink transmission of data, and in a general sense, it refers to the devices that provide power to the outside world for data downlink.
UFP（Upstream Facing Port）： The upstream port can be understood as a device, and UFP takes power from VBUS and can provide data. Typical devices are USB flash drives and portable hard drives.
DRP（Dual Role Port）： Dual role port, similar to the previous OTG, DRP can be used as both DFP (Host) and UFP (Device), and can dynamically switch between DFP and UFP. A typical DRP device is a laptop. The role of the device when it is first connected is determined by the Power Role of the port (as described later); Subsequent changes can also be made through the switch process (if USB PD protocol is supported).
The power supply (or reception) status of USB PORT, USB Type-C divides the port into Source Sink。
Source： Powered by VBUS or VCONN.
Sink： Receive power through VBUS or VCONN.
DRP(Dual-Role-Power)： It can be used as both a source and a sink. Whether to use it as a Source or Sink depends on the configuration after the device is connected.
The connection process between Source and Sink
In the case of universal USB for Source and Sink, the typical process for configuring interfaces is as follows: first, check the effective connections between ports (including determining cable direction, source/receiver, and DFP/UFP relationship). Secondly, the ability to detect cables. Reconnect USB power supply (negotiate USB power transfer, select power mode, battery charging cable, etc.)
USB4 E-mark Chip Science Popularization
The specifications before Type C (TypeA, TypeB, etc.) focused on the "hard" features of the USB interface, such as the number of signals, interface form, electrical characteristics, and so on. On the basis of defining the "hard" characteristics of the USB interface, TypeC has added some "soft" content. The USB interface (only referring to TypeC) has freed itself from its subordinate relationship with USB and become a new specification that can be on par with the USB specification. After the USB upgrade to version 3.1, all physical interfaces adopted the Type C structure, and the actual application of the 3.1 standard USB Type-C cable structure was not unified, causing a lot of chaos. Until 2019, the association set a threshold to standardize their functionality and electrification performance. If products want to support 5A high current, USB 3.0 or higher transmission speed, and video output function, they need to be equipped with E-Marker chips. E-mark， The full name is: Electronically Marked Cable， A USB Type-C active cable packaged with an E-Marker chip, DFP and UFP can use PD protocol to read the cable's properties, including power transmission capability, data transmission capability, ID and other information. Simply put, if the Type-C data line carries an E-Marker chip (which we call an electronic tag), this chip can communicate with the USB port through the USB Power Supply Specification 2.0 BMC protocol. The electronic tag cable can be powered by VCONN or directly by Vbus, with a maximum power consumption of 70mW.
USB Type-C cable compatible with USB 3.1, 100W power cable. Any cable capable of carrying a power of over 60W must have an electronic tag and be able to communicate with the DFP port. If a cable with an electronic tag is inserted into a socket that does not support USB power specification 2.0, its behavior is exactly the same as that of a standard passive cable.
E-Marker (electronically marked cable) can be simply understood as an electronic tag for Type-C cables. The E-Marker chip can read the functional attributes of the cable settings, such as power transmission, data transmission, video transmission, and ID. Based on this, the output terminal can adjust the matching voltage/current or audio and video signals according to the connected devices such as mobile phones or displays. past times, E-Marker chips have always needed to be imported, Cypress and Intel both have strong products with E-Marker chips, and Apple once customized the E-Marker USB 4 chip JHL 7040 from Intel for use on the Thunderbolt interface. In recent years, with the efforts of some domestic companies, domestically produced E-maker chips that can support USB 4 have also begun to be commercialized
Use it. In October 2020, Chengdu Yichong Semiconductor launched the first E-Marker chip CPS 8821 in mainland China and the fifth in the world to pass USB-IF USB 4 certification. Since then, many companies have also launched related products on USB 4 E-Marker.
Currently, some E-Marker product models that support USB4 have been released
Brand Name Chip Model
Cypress CPD2103
Intel JHL7040
Weifeng Electronics VL153
Easy to charge semiconductor CPS8821
Yingjixin IP2133
The first principle of using E-mark: If you want to provide voltage exceeding 5V or current exceeding 3A through the USB TYPE-C interface, you must use a TYPE-C interface chip to implement the USB PD protocol
Use the second principle of E-mark: If your device uses 5V voltage and does not exceed 3A current. That depends on the power supply characteristics and data transmission characteristics of the device itself. If the device only supplies power to the outside or only accepts power from the other party, and the power supply role is paired with the data transmission role by default (i.e. the power supply is HOST and the power consumption is Slave or device), then you do not need a TYPE-C chip
The third principle of using E-mark: These two principles are used to determine whether TYPE-C chips are needed on the device, and another point of concern is whether E-MARKER chips are needed on the C-C transmission line. This criterion is whether the current will exceed 3A during use? If it does not exceed, it may not be necessary, For A to C and B to C cables, it depends on whether the Battery Charging protocol needs to be implemented. If it needs to be implemented, LDR6013 can be used, which brings the advantage of being able to charge and transmit data, avoiding the problem of adapters that do not comply with the Battery Charging protocol being unable to charge Apple devices.
All USB full-featured Type-C cables should be electronically labeled. EMarker is an element in an electronic tag cable that responds to identification commands issued by USB PD and returns information about the cable, such as its current carrying capacity, performance, manufacturer identification, supported sstx/ssrx channels, etc. The power consumption of the electronic tag cable itself generally comes from Vconn, and Vbus may also be used.